1. Field of the Invention
The present invention relates to an analog front-end processing apparatus and a related method for pin-sharing, and more particularly, to an analog front-end processing apparatus and a related method for having all negative signals fixed at a reference voltage and improving its internal sample and hold circuits.
2. Description of the Prior Art
Display system chips, such as televisions and liquid crystal display (LCD) screens, usually have an analog front-end circuit for converting analog signals (such as R, G, and B) into digital signals for displaying images. In practice, the analog signals are usually single-ended signals. But for noise considerations, the display system chip will adopt differential signals in signal processing, and thus the received single-ended signals must be converted into differential signals within the chip. Because the DC level of each signal is different from each other, AC-coupling techniques are used to input AC components of the signals into the display system chip. And then the DC level of each signal is redistributed after AC coupling capacitors.
Common approach of the DC level redistribution, taking the DC level redistribution of image signals as an example, is that firstly fix the DC levels of positive signals (such as R+, G+, and B+) of differential signals at their corresponding target positive voltages, and then fine-tune the DC levels of negative signals (such as R−, G−, and B−) of the differential signals to their corresponding target negative voltages to therefore determine the DC levels of the differential signals. Due to the signal range of each positive signal being different, the target negative voltage of each channel would be different. As a result, the negative pins of the negative signals cannot be shared, and the number of the negative pins is equal to the number of the positive signals, which is not economic in consideration of cost.